Hearing Flashcards
what is the function of hearing
- Distinguishing different sounds
- Localization
Language
what does language do
- Production
- Comprehension
what are the 3 structures that allow hearing to take part
- Outer ear
- Middle ear
- Inner ear
what is the function of the central auditory nervous system
- Electrochemical action potentials
- Information processing
what is the outer ear divided into
Pinna
Ear Canal
what is the mode of operation of the outer ear
Air Vibration
what is the function of the outer ear
1) Protect ear
2) Localise
3) AMPLIFY
what is the middle ear divided into
Tympanic Membrane
Eustachian Tube
Small bones - stapes incus and malleus
what is the mode of operation of the middle ear
Mechanical Vibration
what is the function of the middle ear
1) IMPEDANCE MATCHING
2) Equalise pressure – Eustachian tube prevents a standing pressure difference on either side of the eardrum that would compromise function
3) Stimulate inner ear– the arrangement of ossicles transmits vibrational energy to the oval window, preventing it from being reflected away from the surface of the inner ear
what are the divisions of the inner ear
Cochlea
Semilunar canals
what is the mode of operation of the inner ear
Hydrodynamic (fluid)
Electrochemical
what is the function of the inner ear
1) Sound filtering
2) Signal Transduction
what is impedance matching
overcome the acoustic impedance between the air in outer ear and the fluid in the inner ear.
What are the two ways in which impedance matching is done
1) Transmission of Vibration through the Malleus, Incus and stapes, vibrations from transmitted ear to the bones causes a vibration ratio, so the malleus from the tympanic membrane moves 1mm the stapeus will move 1.3mm therefore there is a higher movement generated for fluid to move
2) Tympanic Membrane to Oval window area difference 22:1 this leads to Higher pressure generated over smaller area, these can overcome the high impedance of the cochlea and make the cochlear vibrate
what is between the middle ear to the outer ear
- it is all air
- but when you get to the cochlea (inner ear) there is fluid, the fluid is harder to get it to vibrate than the air therefore there is a higher resistance (impedance)
what part of the ear controls the transmission of sound
cochlear
what are the two parts of transmission of sound
- Frequency Transmission (High or Low Pitch) - Hz
- Amplitude Transmission ( Loud or Soft) - dB
describe how the cochlear transmits sound
- Cochlea is a tube turn 2 and ¾ turns
- Vibrations pass on as fluid movement via oval window
- Fluid movement converted to electrochemical information by cochlear cells
- Transmitted to brain via nerve
what are the 3 canals in the cochlea
- scala tympani (perilymph)
- cochlear duct (endolymph)
- scala vestibuli
how is the 3 canals separated
- The canal on the outside is the Scala tympani this is separated from the middle canal, the cochlear duct, by the basilar membrane, the cochlear duct is separated from the inner canal, Scala vestibuli, by the vestibular membrane
what are the inner and outer hair cells attached to
- Within the cochlear duct we have the Tectorial membrane from which the Outer air cells and Inner Hair Cells protrude.
- The inner cells are attached to the membrane and outer cells are suspended between supporting cells
describe the entire part of the cochlea
Entire organ: Organ of Corti
- Basilar membrane is floor
- Tectorial membrane is roof
- In between is the hair cells
what is within the cochlear duct
Tectorial membrane
what is in the organ of cortic
Outer and Inner Hair Cells
what are the outer hair cells involved in
- 3 Rows
– Suspended between supporting cells - Auditory Discrimination - they increase there sensitivities to specific frequencies of sounds
– amplify sound + discriminate sounds,
what are the inner hair cells involved in
- 1 Row
- Attached to the basilar membrane
- Frequency tuning
– split sound into different frequencies as they vibrate at different points along the membrane due to different frequencies
how do the inner and outer hair cells convert signals to electrical signals
Convert signals to electrical signals via K+ Channels
- converted to signals for the cochlear nerve